electronic supplementary information synthesis and properties of … · 2020-04-16 · 1 electronic...

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Electronic Supplementary Information Synthesis and Properties of Hypervalent Electron-rich Pentacoordinate Nitrogen Compounds Chenting Yan, a Masato Takeshita, a Jun-ya Nakatsuji, a Akihiro Kurosaki, a Kaoko Sato, a Rong Shang,*a Masaaki Nakamoto, a Yohsuke Yamamoto,*a Yohei Adachi,b Ko Furukawa, c Ryohei Kishi, d Masayoshi Nakano d,e

a. Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526, Japan b. Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526, Japan c. Center for Coordination Research Facilities, Institute for Research Promotion, Niigata University, 8050 Ikarashi 2-no-cho, Nishi-ku, Niigata 950-2181, Japan d. Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan e. Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan

Contents

1. Experimental section

2. UV-Vis, EPR, CV spectra

3. Crystal Structure Determination

4. DFT calculation

5. p-donating methoxy derivative (2Mec)

6. NMR spectra

7. References

Electronic Supplementary Material (ESI) for Chemical Science.This journal is © The Royal Society of Chemistry 2020

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1. Experimental section

Experimental Procedures

Instrumentation and Chemicals All manipulations were performed under Ar or N2 atmosphere by using standard Schlenk or glove box techniques. All the solvents were dried prior to use. Column chromatography was carried out using Merck silica gel 60 and KANTO CHEMICAL silica gel 60N. The 1H NMR (400 MHz), 13C NMR (100 MHz) and 19F NMR (376 MHz) spectra were recorded using a JEOL EX-400 spectrometers. The chemical shift (d) are reported from the internal CHCl3 for 1H (δ 7.26) and from the internal CDCl3 for 13C (δ 77.0) and from the internal CFCl3 for 19F (δ 0.00). Mass spectra were recorded with a Thermo Fisher Scientific samples. The X-ray crystal structural analysis was performed using a Bruker APEX II Ultra. The DFT calculations were performed using the Gaussian 16 program package.

1.1 Synthesis of 2-Bromo-5-tert-butyl-1,3-dimethylbenzene (b)

In a 250 mL round-bottom flask equipped with a magnetic stir bar and an addition funnel were added 5-tert-butyl-m-xylene (91.0 mL, 480 mmol) and iron powder (1.00 g, 1.36 mmol) to 75 mL of chloroform. The solution was cooled to 0 °C. A solution of bromine (27.5 mL, 525 mmol) in 25 mL of solution of chloroform was added dropwise via the addition funnel. The reaction was stirred for 3 h at room temperature and then poured into a cold solution of dilute aqueous NaOH (~1 M). The mixture was separated, and the aqueous layer was washed several times with CH2Cl2. The combined organic layers were dried with MgSO4, filtered, and concentrated to a clear oil, which became a white solid upon standing. The crude solid was recrystallized from ethanol to give 105 g (437 mmol, 90% yield) of the title compound. 1H NMR (400 MHz, CDCl3) δ (ppm) 7.11 (s, 2H), 2.43 (s, 6H), 1.31 (s, 9H). 13C NMR (100 MHz, CDCl3) δ (ppm) 149.8, 137.8, 125.6, 124.6, 34.3, 31.4, 24.2. MS (GC-EI): [M]+ C12H17Br Calcd for: 240.05136 Found: 240.05148. M.P.: 48.5-49.8 °C. 1.2 Synthesis of 2-Bromo-5-tert-butyl-isophthalic Acid (c)

In a 500 mL three-necked round-bottom flask equipped with a mechanical stirrer and a reflux condenser was added 2-bromo-5-tert-butyl-1,3-dimethylbenzene (24.5 g, 101 mmol) and KMnO4 (33.7 g, 214 mmol), dispersed in 200 mL of a 1:1 mixture of tert-butyl alcohol and water. The reaction mixture was heated to reflux for 1 h. After the mixture was cooled to room temperature, more KMnO4 (33.2 g, 210 mmol) was added and the reaction mixture was refluxed for an additional 20 h. After the mixture was cooled to room temperature, the reaction was filtered through Celite and the filtrate was reduced by 1/3. The solution was acidified with concentrated HCl. The resulting white precipitate was collected by filteration and dissolved in aqueous NaHCO3. The aqueous layer was washed with ether to remove any residual organics. The aqueous layer was then acidified with concentrated HCl and the precipitate was collected and oven-dried (~80 °C) overnight to give 29.6 g (98.3 mmol, 97% yield) of the title compound. 1H NMR (400 MHz, DMSO) δ (ppm) 13.60 (s, 2H), 7.68 (s, 2H), 1.28 (s, 9H).13C NMR (100 MHz, DMSO) δ (ppm) 168.3, 150.7, 136.6, 127.8, 113.3, 34.6, 30.6. MS(ESI) m/z [M-H]- C12H12O4Br Calcd for: 298.99344 Found: 298.99225. M.P.:236.4-239.9 °C. 1.3 Synthesis of Dimethyl 2-Bromo-5-tert-butyl-isophthalate (1Me)

In a 100 mL three-necked round-bottom flask equipped with a magnetic stir bar and a reflux condenser was added 2-bromo-5-tert-butyl-isophthalic acid (8.0 g, 26.6 mmol), in 57.0 mL of methanol and 6 mL of H2SO4. The reaction mixture was heated to reflux for 24 h and neutralized with NaHCO3 at 0 °C. The aqueous solution was washed several times with ether. The combined organic layers were dried over MgSO4, filtered, and concentrated. Recrystallization from hexane gave 7.13 g (21.6 mmol, 82% yield) 1Me as white solid. 1H NMR (400 MHz, CDCl3) δ (ppm) 7.68 (s, 2H), 3.93 (s, 6H), 1.30 (s, 9H). 13C NMR (100 MHz, CDCl3) δ (ppm) 167.6, 150.9, 135.1, 129.6, 115.8, 77.48, 52.8, 34.8, 31.0. MS(ESI) m/z [M+Na]+ C18H25O4BrNa Calcd for: 407.08284 Found: 407.08310. M.P.:100.3-101.1 °C.

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1.4 Synthesis of diisopropyl 2-bromo-5-(tert-butyl) isophthalate (1iPr) In a 100 mL two-necked round-bottom flask equipped with a magnetic stir bar and a reflux condenser was added 2-bromo-

5-tert-butyl-isophthalic acid (8.0 g, 26.6 mmol), in 57.0 mL of isopropanol and 6.0 mL of H2SO4. The reaction mixture was heated to reflux for 24 h and neutralized with NaHCO3. The aqueous solution was washed several times with diethyl ether. The combined organic layers were dried over MgSO4 and filtered. Removal of solvent gave 7.96 g (24.4 mmol, 78% yield) 1iPr as colorless oil. 1H NMR (400 MHz, CDCl3) δ (ppm) 7.59 (s, 2H), 5.32 – 5.22 (m, 2H), 1.38 (d, J = 4 Hz, 12H), 1.30 (s, 9H). 13C NMR (100 MHz, CDCl3) δ (ppm) 166.9, 150.8, 135.9, 128.9, 115.0, 70.0, 34.8, 30.9 21.8. MS(ESI) m/z [M+Na]+ C14H17O4BrNa Calcd for: 351.02024 Found: 351.02075. General Procedure for Ullmann Coupling

The para-substituted diarylamine (1.0-1.2 eq. to the tridentate ligand precursor), dimethyl 2-bromo-5-tert-butyl-isophthalate (1Me) or diisopropyl 2-bromo-5-(tert-butyl)isophthalate (1iPr), potassium carbonate (1.5 eq. to the tridentate ligand precursor), and copper bronze (10-20 mol% eq. to the tridentate ligand precursor) were combined with n-Bu2O in a round-bottom flask equipped with a magnetic stir bar and reflux condenser. The reaction was heated to 170-190 °C for 48-96 h under argon. The reaction was filtered, the solvent removed by vacuum distillation, and the residue purified by column chromatography. 1.5 Synthesis of dimethyl 2-(bis(4-chlorophenyl) amino)-5-(tert-butyl) isophthalate (2Mea)

Bis(4-chlorophenyl) amine (7.30 g, 22.3 mmol) was coupled with dimethyl 2-Bromo-5-tert-butyl-isophthalate (1Me) (6.92 g, 21.2 mmol) according to the above Ullmann procedure (120 mL of n-Bu2O is selected for reaction solvent) for 67 h. The crude product was purified by flash chromatography using a 1:1 solution of CH2Cl2/hexane as the eluent to give 5.92 g (10.8 mmol, 51% yield) of the title compound as a pale-yellow solid. 1H NMR (400 MHz, CDCl3) δ (ppm) 7.81 (s, 2H), 7.14 (d, J = 4 Hz, 4H), 6.87 (d, J = 4 Hz, 4H), 3.54 (s, 6H), 1.36 (s, 9H). 13C NMR (100 MHz, CDCl3) δ (ppm) 167.6, 149.8, 145.5, 141.1, 132.1, 131.4, 129.1, 127.3, 123.3, 52.5, 35.0, 31.2. MS(ESI) m/z [M+H]+ C26H26O4NCl2 Calcd for: 486.12334 Found: 486.12350. M.P.:158.0-159.5 °C. 1.6 Synthesis of dimethyl 2-(bis(4-(trifluoromethyl) phenyl) amino)-5-(tert-butyl) isophthalate (2Meb)

Bis(4-(trifluoromethyl) phenyl) amine (610 mg, 2.00 mmol) was coupled with dimethyl 2-Bromo-5-tert-butyl-isophthalate (1Me) (658 mg, 2.00 mmol) according to the above Ullmann procedure (15 mL of n-Bu2O is selected for reaction solvent) for 96 h at 170 °C. The crude product was purified by flash chromatography using a 1:1 solution of CH2Cl2/hexane as the eluent to give 530 mg (0.958 mmol, 48% yield) of the title compound as a white solid: 1H NMR (400 MHz, CDCl3) δ (ppm) 7.91 (s, 2H), 7.45 (d, J = 8 Hz, 4H), 7.04 (d, J = 8 Hz, 4H), 3.53 (s, 6H), 1.38 (s, 9H). 13C NMR (100 MHz, CDCl3) δ (ppm) 167.1, 151.0, 149.2, 140.4, 132.3, 131.7, 126.3 (q, 3J C-F = 10 Hz), 124.4 (q, 1J C-F = 270 Hz), 124.3 (q, 2J C-F = 30 Hz), 121.7, 52.6, 35.1, 31.1. 19F NMR (376 MHz, CDCl3) δ -62.29. MS(ESI) m/z [M+Na]+ C28H25O4NF6Na Calcd for: 576.15800 Found: 576.15784.Elemental analysis: Calcld.: C, 60.76; H, 4.55; N, 2.53; Found: C, 61.14; H, 4.54; N, 2.61. M.P.:183.8-185.2 °C. 1.7 Synthesis of diisopropyl 2-(bis(4-chlorophenyl) amino)-5-(tert-butyl) isophthalate (2iPra)

Bis(4-chlorophenyl) amine (289 mg, 1.21 mmol) was coupled with diisopropyl 2-bromo-5-(tert-butyl) isophthalate (1iPr) (445 mg, 1.15 mmol) according to the above Ullmann procedure for 120 h. The crude product was purified by flash chromatography using a 1:1 solution of CH2Cl2/hexane as the eluent to give 339 mg (0.625 mmol, 54% yield) of the title compound as a pale-yellow solid. 1H NMR (400MHz, CDCl3) δ (ppm) 7.73 (s, 2H), 7.12 (d, J = 8 Hz, 4H), 6.90 (d, J = 8 Hz, 4H), 4.85 (m, 2H), 1.36 (s, 9H), 1.04 (d, J =8 Hz, 12H). 13C NMR (100 MHz, CDCl3) δ (ppm) 166.5, 149.9, 145.3, 140.6, 133.4, 130.4, 128.9, 126.9, 123.1, 69.5, 34.9, 31.2, 21.6. MS(ESI) m/z [M+H]+ C30H34O4NCl2 Calcd for: 542.18594 Found: 542.18604. Elemental analysis: Calcld.: C, 66.42; H, 6.13; N, 2.58; Found: C, 66.80; H, 6.29; N, 2.63. M.P.:144.8-145.2 °C. 1.8 Synthesis of diisopropyl 2-(bis(4-(trifluoromethyl) phenyl) amino)-5-(tert-butyl) isophthalate (2iPrb)

Bis(4-(trifluoromethyl) phenyl) amine (370 mg, 1.21 mmol) was coupled with diisopropyl 2-bromo-5-(tert-butyl) isophthalate (1iPr) (562 mg, 1.45 mmol) according to the above Ullmann procedure for 98 h. The crude product was purified by flash chromatography using a 1:1 solution of CH2Cl2/hexane as the eluent to give 405 mg (0.664 mmol, 55% yield) of the title compound as a pale-yellow solid. 1H NMR (400 MHz, CDCl3) δ (ppm) 7.80 (s, 2H), 7.44 (d, J = 8 Hz, 4H), 7.07 (d, J = 8 Hz, 4H), 4.85 (m, J = 24 Hz, 2H), 1.38 (s, 9H), 0.99 (d, J = 4 Hz, 12H). 13C NMR (100 MHz, CDCl3) δ (ppm) 166.1, 150.9, 149.1, 140.1, 133.4, 130.7, 126.2 (q, 3J C-F = 10 Hz), 124.5 (q, 1J C-F = 270 Hz), 124.0 (q, 2J C-F = 30 Hz), 121.6, 69.7, 35.0, 31.2, 21.4. 19F NMR (376 MHz, CDCl3) δ (ppm) -62.45. MS(ESI) m/z [M+Na]+ C32H33O4NF6Na Calcd for: 632.22060 Found: 632.22052 Elemental analysis: Calcld.: C, 63.05; H, 5.46; N, 2.30; Found: C, 62.99; H, 5.25; N, 2.28. M.P.:188.8-190.1 °C. 1.9 Reaction of 2Mea with (2,4-Br2C6H4)3N•+SbCl6– (3Mea)

A solution of 2Mea (49 mg, 0.10 mmol) and (2,4-Br2C6H4)3N•+SbCl6– (105 mg, 0.100 mmol) in dry CH2Cl2 (5 mL) was stirred for 30 mins at room temperature. The solution color was changed to dark blue. After the removal of solvent, the residue was washed with Et2O to give compound 3Mea as a dark green solid (60 mg, 0.072 mmol, 72%). Purple crystals of 3Mea suitable for X-ray analysis were obtained by recrystallization from CH2Cl2 /hexane under light-shielded condition.

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1.10 Reaction of 2Meb with (2,4-Br2C6H4)3N•+SbCl6– (3Meb) A solution of 2Meb (53 mg, 0.10 mmol) and (2,4-Br2C6H4)3N•+SbCl6– (105 mg, 0.10 mmol) in dry CH2Cl2 (5.0 mL) was stirred

for 30 mins at room temperature. The solution color was changed to dark blue. After the removal of solvent, the residue was washed with Et2O to give compound 3Meb as a dark green solid (65 mg, 0.073 mmol, 73%). 1.11 Reaction of 2iPra with (2,4-Br2C6H4)3N•+SbCl6–(3iPra)

A solution of 2iPra (20 mg, 0.037 mmol) and (2,4-Br2C6H4)3N•+SbCl6– (39 mg, 0.037 mmol) in dry CH2Cl2 (5 mL) was stirred for 30 mins at room temperature. The solution color was changed to dark blue. After the removal of solvent, the residue was washed with Et2O to give compound 3iPra as a dark green solid (20 mg, 0.023 mmol, 62%). Purple crystals of 3iPra suitable for X-ray analysis were obtained by recrystallization from CH2Cl2 / hexane under light-shielded condition. 1.12 Reaction of 2iPrb with (2,4-Br2C6H4)3N•+SbCl6–(3iPrb)

A solution of 2iPrb (35 mg, 0.057 mmol) and (2,4-Br2C6H4)3N•+SbCl6– (60 mg, 0.057 mmol) in dry CH2Cl2 (5 mL) was stirred for 30 mins at room temperature. The solution color was changed to dark blue. After the removal of solvent, the residue was washed with Et2O to give compound 3iPrb as a dark green solid (58 mg, 0.062 mmol, 92%).

2. UV-Vis, EPR and CV spectra

2.1 UV-Vis and Emission spectra UV/Vis spectrum of 0.01 mM solution of 2Mea-b, 2iPra-b and 3Mea-b and 3iPra-b in DCM was recorded on UV-1650PC (SHIMADZU) and HORIBA FluoroMax-4 spectrophotometer in ambient atmosphere at room temperature. The obtained spectrum was illustrated in in Figure S1 and Figure S2.

Figure S1. Absorption spectra (solid) and emission spectra (dashed) of 10-5 M 2Mea-b and 2iPra-b in CH2Cl2 at 25 ℃.

Table S1 Summary of absorption and emission spectra

Compound 2Mea 2Meb 2iPra 2iPrb

Wavelength (nm) Max. e (105 M-1 cm-1)

311 0.237

312 0.266

312 0.136

309 0.339

Quantum Yield 3.22 3.50 9.43 13.95

Lifetime(318nm) (ns) 14.98714 13.47508 7.182881 4.996558

2Mea

O

OMe

O

MeO N

ClCl

t-Bu

Oi-Pr

O

i-PrO

O N

CF3CF3

t-Bu

2iPrb

Oi-Pr

O

i-PrO

O N

ClCl

t-Bu

2iPra

OMe

O

MeO

O N

CF3CF3

t-Bu

2Meb

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Figure S2. Absorption spectra of 10-5 M 2Mea-b and 2iPra-b (solid), 3Mea-b and 3iPra-b (dashed) in CH2Cl2 at 25 ℃.

Table S2 Summary of absorption spectra

Compound 3Mea 3Meb 3iPra 3iPrb

Wavelength (nm) max. e (105 M-1 cm-1)

745 0.212

688 0.696

739 0.197

681 0.305

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2.2 Electron paramagnetic resonance (EPR)

The electron paramagnetic resonance (EPR) spectra of 3Mea-b and 3iPra-b were measured by using a Bruker ELEXSYS E500 spectrometer at room temperature. All samples were prepared as a 10–5~10–4 mM solution in CH2Cl2. After freeze-pump-thaw cycles, the solution sample in a quartz tube was sealed by frame. Spectral simulation was performed using EasySpin, which is a MATLAB toolbox meant for this.

Table S3 Spin Hamiltonian parameters estimated from the spectral simulation for 3Mea-b and 3iPra-b. The number of equivalent protons is noted in brackets.

3Mea 3Meb 3iPra 3iPrb Equivalency

g 2.0042 2.0028 2.0042 2.0035 –

AN1 / MHz 26.8 29.9 27.2 29.9 1

AH1 / MHz 7.2 14.7 7.7 14.4 4

AH2 / MHz 4.6 7.5 4.5 7.4 4

ACl / MHz <1 – <1 – 2

AF / MHz – 4.1 – 3.9 6

O

Oi-Pr

O

i-PrO N1

Cl Cl

t-Bu

H2

H1

OMe

O

MeO

O N1

Cl Cl

t-Bu

H2

H1

OMe

O

MeO

O N1

CF3 CF3

t-Bu

H2

H1

O

Oi-Pr

O

i-PrO N1

CF3 CF3

t-Bu

H1

H2

3Mea 3Meb 3iPrb3iPra

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2.3 Cyclic voltammetry

Cyclic voltammetry measurement of 2Mea-b and 2iPra-b (1.0 mM) was performed by using an ALS 600D potentiostat / galvanostat in DCM solution containing 100 mM of [nBu4N] [PF6] with a scan rate of 100 mV/s in ambient atmosphere at room temperature. A three-electrode cell, which was equipped with a Pt disk working electrode, a Pt wire counter electrode, and SCE reference electrode, was used. The half wave potentials of 2Mea-b and 2iPra-b was compensated with that of ferrocene/ferrocenium redox cycle, which is +0.46 V (vs. SCE). The cyclic voltammogram is illustrated in Figure S3.

Figure S3. Cyclic voltammogram of a 1.0 mM solution of 2Mea-b and 2iPra-b in DCM using 100 mM of [nBu4N] [PF6] as the supporting electrolyte.

Table S4. Formal potentials of neutral compounds.

Compound Epa / v Epc / v Formal potentials / v

2Mea 1.243 1.149 1.196

2Meb 1.541 1.430 1.485

2iPra 1.225 1.129 1.177

2iPrb 1.538 1.417 1.477

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3. Crystal Structure Determination

Crystals suitable for X-ray structural determination were mounted on a Bruker SMART APEXII CCD diffractometer. Samples were irradiated with graphite monochromated Mo-Kα radiation (λ= 0.71073 Å) at 173 K for data collection. The data were processed using the APEX program suite. All structures were solved by the SHELXT program (ver. 2014/5). Refinement on F2 was carried out by full-matrix least-squares using the SHELXL in the SHELX software package (ver. 2014/7) [1] and expanded using Fourier techniques. All non-hydrogen atoms were refined using anisotropic thermal parameters. The hydrogen atoms were assigned to idealized geometric positions and included in the refinement with isotropic thermal parameters. The SHELXL was interfaced with ShelXle GUI (ver. 742) for most of the refinement steps. [2] The pictures of molecules were prepared using Pov-Ray 3.7.0.[3] The crystallographic data are summarized in Table S5. CCDC-1945530-1945536 contain the supplementary crystallographic data for this paper.

Table S5. Selected X-ray parameter of 1Me ,2Mea-b, 2iPra-b, 3Mea and 3iPra.

CCDC

1Me 1945530

2Mea 1945531

2Meb 1945532

3Mea 1945533

2iPra 1945534

2iPrb 1945535

3iPra 1945536

Formula C14H17BrO C26H25Cl2NO4 C28H25F6NO4 C26H25Cl8NO4Sb C30H33Cl2NO4 C32H33F6NO4 C30H33Cl8NO4Sb

Mol wt 329.18 486.37 553.49 820.82 542.47 609.59 876.92

Crystal system Orthorhombic Orthorhombic Monoclinic Monoclinic Triclinic Triclinic Monoclinic

Space group Pbcn Pbca P21/n P21/n P-1 P-1 P21/n

a, Å 21.874(5) 18.3830(16) 11.7241(3) 11.6398(8) 11.840(2) 10.0890(4) 12.156(3)

b, Å 15.366(3) 13.3271(12) 12.3047(3) 18.4868(13) 14.543(3) 11.8293(5) 15.548(3)

c, Å 8.915(3) 20.1022(18) 18.3432(5) 16.2027(11) 18.231(3) 13.7884(6) 19.482(4)

α, deg 90 90 90 90 97.047(3) 97.5670(10) 90

β, deg 90 90 100.0770(10) 109.070(3) 105.059(3) 107.7540(10) 90.770(4)

γ, deg 90 90 90 90 102.364(3) 95.2740(10) 90

V, Å3 2996.4(12) 4924.9(8) 2605.40(12) 3295.2(4) 2907.6(9) 1538.29(11) 3681.6(13)

Z 8 8 4 4 4 2 4

Dcalc, Mg/m3 1.459 1.312 1.411 1.655 1.239 1.316 1.582

Abs coeff, mm−1 2.750 0.296 0.122 1.518 0.257 0.110 1.365

F(000) 1344 2032 1144 1628 1144 636 1756

Temp, K 173(2) 173(2) 173(2) 173(2) 173(2) 173(2) 173(2)

Reflections 33840 44338 12410 15559 14070 18837 20884

Independent 3737 4249 4485 5614 10099 7482 8431

Rint 0.0358 0.0348 0.0222 0.0246 0.0334 0.0452 0.0860

Parameters 177 303 413 366 689 451 411

R1 [I > 2σ(I)] 0.0272 0.0384 0.0385 0.0312 0.0610 0.0406 0.0573

wR2 (all data) 0.0727 0.1076 0.1032 0.0800 0.2302 0.1114 0.1058

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Figure S4. Molecular structures of 1Me obtained from single-crystal X-ray diffraction analysis. Thermal ellipsoids are displayed at 30% probability. Hydrogen atoms are omitted for clarity.

Figure S5. Molecular structure of 2Mea-b, 2iPra-b, 3Mea and 3iPra (Side-view) obtained from single-crystal X-ray diffraction analysis. Thermal ellipsoids are displayed at 30% probability. Hydrogen atoms are omitted for clarity.

2iPra3iPra(radical cation)

2iPrb

2Mea 2Meb3Mea(radical cation)

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Figure S6. The difference of N-O bond length between 2Mea-b, 2iPra-b, 3Mea and 3iPra: average N-O distances (blue); differences of NO distance (orange).

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4. DFT calculation

4.1 Optimized geometries

Geometry optimizations were performed at the RCAM- and UCAM-B3LYP-D3/def2-SVP, B3PW91/6-31G(d) and UB3PW91/6-31G(d), B3LYP/6-31G(d,p) and UB3LYP/6-31G(d,p), B3LYP/cc-pVDZ and UB3LYP/cc-pVDZ levels for 2 and 3, respectively, using Gaussian 09 program package. Here, IEF-PCM method was employed in order to consider solvent (CH2Cl2) effects.

Single point calculations at the RCAM- and UCAM-B3LYP-D3/def2-SVP levels were performed using ORCA 4.2 program package [4], where C-PCM method was employed for solvent effects. Natural population analysis (NPA) and atoms in molecules (AIM) analysis were performed using the NBO 6.0[5] and Multiwfn 3.6[6] program packages, respectively. For the domain-based local pair-natural orbital coupled-cluster singles and doubles (DLPNO-CCSD)/def2-SVP calculations [7], the options “NormalPNO” and “VeryTightSCF” as well as def2-SVP/C and def2/JK auxiliary basis were employed.

Table S6. Selected calculated bond lengths (Å), angles and dihedral angles [°], and net NPA charges q [–] for 2Mea-b, 2iPra-b, 3Mea and 3iPra at the RCAM- and UCAM-B3LYP-D3/def2-SVP levels in 2 and 3, respectively.

Parameters Ionic radical Neutral Ionic radical Neutral

3Mea 2Mea 2Meb 3iPra 2iPra 2iPrb

Coord. (CO) (OMe) (CO) (OiPr) (CO) (CO)

N-O1 2.684 2.734 2.795 2.673 2.885 2.882

N-O2 2.686 2.734 2.802 2.676 2.889 2.886

N-OAve 2.684 2.734 2.798 2.674 2.887 2.884

N-C1 1.435 1.417 1.420 1.439 1.416 1.419

N-C2 1.387 1.405 1.403 1.387 1.408 1.405

N-C3 1.388 1.405 1.401 1.388 1.407 1.404

SNa 360.0 360.0 360.0 360.0 360.0 360.0

FOCCO 39.1 67.2 56.3 47.0 73.6 74.4

q(N) –0.270 –0.502 –0.497 –0.275 –0.498 –0.493

q(O1) –0.645 –0.648 –0.637 –0.602 –0.643 –0.643

q(O2) –0.645 –0.648 –0.638 –0.602 –0.643 –0.643

q(C1) 0.178 0.212 0.217 0.165 0.214 0.208

q(C2) 0.170 0.175 0.198 0.176 0.173 0.194

q(C3) 0.171 0.175 0.200 0.174 0.173 0.195

O2O1 N

C2

X

C3

X

C1

t-Bu

N

t-Bu

O1 O2

C3

X

C2

X

Front View Side ViewΦ

General numbering scheme

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Table S7. Selected calculated bond lengths (Å), angles and dihedral angles [°] for 2Mea-b, 2iPra-b, 3Mea and 3iPra at the B3PW91/6-31G(d) in 2 and UB3PW91/6-31G(d) in 3, respectively.




N-O1 2.727 2.795 2.871 2.798 2.884 2.855

N-O2 2.727 2.796 2.873 2.860 2.870 2.858

N-OAve 2.727 2.796 2.872 2.820 2.877 2.857

N-C1 1.436 1.42 1.418 1.432 1.416 1.419

N-C2 1.393 1.409 1.408 1.394 1.410 1.406

N-C3 1.393 1.409 1.407 1.394 1.409 1.407

SNa 360.0 360.0 360.0 360.0 360.0 360.8

FOCCO 45.3 69.1 66.5 74.2 69.2 65.4

Table S8. Selected calculated bond lengths (Å), angles and dihedral angles [°] for 2Mea-b, 2iPra-b, 3Mea and 3iPra at the B3LYP/6-31G(d,p) in 2 and UB3LYP/6-31G(d,p) in 3, respectively.




N-O1 2.733 2.801 2.876 2.788 2.885 2.869

N-O2 2.734 2.802 2.877 2.845 2.892 2.876

N-OAve 2.733 2.801 2.876 2.816 2.888 2.872

N-C1 1.443 1.426 1.424 1.440 1.422 1.425

N-C2 1.398 1.415 1.413 1.399 1.415 1.413

N-C3 1.398 1.415 1.413 1.399 1.416 1.412

SNa 360.0 360.0 360.0 360.0 360.0 360.0

FOCCO 43.7 68.6 65.3 70.0 69.5 67.2

Table S9. Selected calculated bond lengths (Å), angles and dihedral angles [°] for 2Mea-b, 2iPra-b, 3Mea and 3iPra at the B3LYP/cc-pVDZ in 2 and UB3LYP/cc-pVDZ in 3, respectively.




N-O1 2.722 2.771 2.847 2.773 2.857 2.835

N-O2 2.723 2.772 2.848 2.824 2.866 2.844

N-OAve 2.722 2.771 2.847 2.798 2.861 2.839

N-C1 1.444 1.428 1.426 1.442 1.423 1.427

N-C2 1.398 1.415 1.414 1.399 1.416 1.413

N-C3 1.399 1.415 1.413 1.399 1.415 1.412

SNa 360.0 360.0 360.0 360.0 360.0 360.0

FOCCO 38.3 59.5 57.6 62.8 62.7 58.8

13

4.2 TD-DFT calculation

TDDFT calculation was carried out at the B3LYP/cc-pVDZ level in 2 and at UB3LYP/cc-pVDZ level in 3 using the Gaussian 09 program. CH2Cl2 for solvent effect.

Figure S7. TD-DFT of optimized 2Mea-b and 2iPra-b at the B3LYP/cc-pVDZ level. Experimental absorption (blue) and Oscillator strength (black).

2iPra

2iPra HOMO 143 LUMO 144

Excited State 1: Singlet-A 3.1253 eV 396.71 nm f=0.0431 <S**2>=0.000143 ->144 0.70139


Excited State 3: Singlet-A 4.0411 eV 306.81 nm f=0.2400 <S**2>=0.000143 ->146 0.60353143 ->147 -0.34482

Excited State 4: Singlet-A 4.0763 eV 304.16 nm f=0.2169 <S**2>=0.000143 ->146 0.35085143 ->147 0.60431


Excited State 6: Singlet-A 4.7239 eV 262.46 nm f=0.0244 <S**2>=0.000136 ->145 0.15938137 ->144 -0.19568138 ->144 -0.12125138 ->145 0.11356139 ->144 -0.26758140 ->145 -0.19364141 ->144 0.50291142 ->144 -0.10948142 ->145 0.11591

2Mea

2Mea HOMO 127 LUMO 128Excited State 1: Singlet-A 3.1339 eV 395.62 nm f=0.0346 <S**2>=0.000

127 ->128 0.70095Excited State 2: Singlet-A 3.2374 eV 382.97 nm f=0.1086 <S**2>=0.000


127 ->130 0.48970127 ->131 0.49809

Excited State 4: Singlet-A 4.0805 eV 303.85 nm f=0.3753 <S**2>=0.000127 ->130 0.50091127 ->131 -0.48364


Excited State 6: Singlet-A 4.7402 eV 261.56 nm f=0.0118 <S**2>=0.000121 ->128 -0.14620122 ->128 -0.12228122 ->129 0.16698123 ->128 -0.24082124 ->129 0.33066125 ->128 0.36901126 ->128 -0.17813126 ->129 0.28509

2Meb

2Meb HOMO 143 LUMO 144Excited State 1: Singlet-A 3.2665 eV 379.56 nm f=0.0442 <S**2>=0.000




142 ->146 -0.10824143 ->147 0.68630

Excited State 5: Singlet-A 4.5535 eV 272.28 nm f=0.0290 <S**2>=0.000141 ->146 -0.12622142 ->145 -0.10370143 ->148 0.65771143 ->149 0.11286

Excited State 6: Singlet-A 4.7144 eV 262.99 nm f=0.0156 <S**2>=0.000136 ->145 0.16362137 ->144 0.14972139 ->144 -0.16657139 ->145 0.11536140 ->144 -0.29742141 ->145 0.19374142 ->144 0.50254

2iPrb

2iPrb HOMO 159 LUMO 160Excited State 1: Singlet-A 3.2910 eV 376.74 nm f=0.0523 <S**2>=0.000




158 ->162 0.10096159 ->163 0.68683

Excited State 5: Singlet-A 4.5454 eV 272.77 nm f=0.0265 <S**2>=0.000157 ->162 -0.11625159 ->164 0.66042159 ->165 -0.10638

Excited State 6: Singlet-A 4.7088 eV 263.30 nm f=0.0154 <S**2>=0.000152 ->161 -0.17221153 ->160 -0.16031155 ->160 -0.13010156 ->160 -0.31352157 ->161 0.19257158 ->160 0.50540

14

Figure S8. TD-DFT of optimized 3Mea-b and 3Pra-b at the UB3LYP/cc-pVDZ level. Experimental absorption (blue) and Oscillator strength (black).

3Mea

3Mea HOMO 126 SOMO 127 LUMO 128Excited State 1: 2.022-A 1.7870 eV 693.81 nm f=0.3020 <S**2>=0.772

127A ->130A 0.11635126B ->127B 0.98763

Excited State 2: 2.029-A 1.8886 eV 656.47 nm f=0.0204 <S**2>=0.779122B ->127B -0.30756125B ->127B 0.94095

Excited State 3: 2.026-A 2.0854 eV 594.52 nm f=0.0051 <S**2>=0.776122B ->127B 0.60043123B ->127B -0.32339124B ->127B 0.69966125B ->127B 0.18288

Excited State 4: 2.032-A 2.1222 eV 584.22 nm f=0.0038 <S**2>=0.783120B ->127B -0.15661121B ->127B 0.87331123B ->127B -0.39063124B ->127B -0.21555

Excited State 5: 2.027-A 2.1694 eV 571.52 nm f=0.0229 <S**2>=0.778121B ->127B 0.43403122B ->127B -0.19426123B ->127B 0.69022124B ->127B 0.51256125B ->127B -0.15934

Excited State 6: 2.030-A 2.2034 eV 562.70 nm f=0.0588 <S**2>=0.780121B ->127B 0.11656122B ->127B 0.70196123B ->127B 0.50029124B ->127B -0.43076125B ->127B 0.20796

3iPra

3iPra HOMO 142 SOMO 143 LUMO 144Excited State 1: 2.021-A 1.7562 eV 705.96 nm f=0.2439 <S**2>=0.771

140B ->143B -0.12106141B ->143B -0.17832142B ->143B 0.96484

Excited State 2: 2.027-A 1.8644 eV 665.01 nm f=0.0854 <S**2>=0.777138B ->143B -0.28012140B ->143B -0.21669141B ->143B 0.91464142B ->143B 0.14691

Excited State 3: 2.027-A 1.9355 eV 640.58 nm f=0.0406 <S**2>=0.777137B ->143B -0.12906138B ->143B 0.16597140B ->143B 0.92676141B ->143B 0.24452142B ->143B 0.15799

Excited State 4: 2.032-A 2.0830 eV 595.21 nm f=0.0242 <S**2>=0.782138B ->143B 0.90863139B ->143B -0.21603140B ->143B -0.23293141B ->143B 0.23759

Excited State 5: 2.032-A 2.1455 eV 577.89 nm f=0.0015 <S**2>=0.782136B ->143B 0.19617137B ->143B 0.94659139B ->143B 0.17992140B ->143B 0.12431

Excited State 6: 2.023-A 2.2194 eV 558.63 nm f=0.0025 <S**2>=0.774137B ->143B -0.17120138B ->143B 0.23024139B ->143B 0.95468

3iPrb HOMO 158 SOMO 159 LUMO 160Excited State 1: 2.029-A 1.6377 eV 757.08 nm f=0.0154 <S**2>=0.779

153B ->159B 0.15287154B ->159B 0.11220158B ->159B 0.97382

Excited State 2: 2.031-A 1.8441 eV 672.31 nm f=0.0062 <S**2>=0.781153B ->159B 0.28799154B ->159B 0.26603156B ->159B 0.90178158B ->159B -0.13597

Excited State 3: 2.035-A 1.8828 eV 658.50 nm f=0.0123 <S**2>=0.785152B ->159B -0.19333153B ->159B -0.33712154B ->159B 0.40874155B ->159B 0.31643157B ->159B 0.75540

Excited State 4: 2.030-A 1.9233 eV 644.64 nm f=0.0016 <S**2>=0.781153B ->159B -0.21604154B ->159B 0.39907155B ->159B 0.64276157B ->159B -0.60521

Excited State 5: 2.034-A 2.0457 eV 606.08 nm f=0.0790 <S**2>=0.785153B ->159B 0.60933154B ->159B 0.62466155B ->159B -0.17676156B ->159B -0.41090158B ->159B -0.14352

Excited State 6: 2.039-A 2.0599 eV 601.90 nm f=0.1917 <S**2>=0.790159A ->162A 0.11400153B ->159B 0.57887154B ->159B -0.41106155B ->159B 0.64872157B ->159B 0.20304

3Meb HOMO 142 SOMO 143 LUMO 144Excited State 1: 2.030-A 1.6575 eV 748.02 nm f=0.0210 <S**2>=0.780

137B ->143B 0.21085140B ->143B -0.13037142B ->143B 0.95931

Excited State 2: 2.031-A 1.8563 eV 667.90 nm f=0.0014 <S**2>=0.781137B ->143B -0.20948138B ->143B -0.17392140B ->143B 0.87189141B ->143B -0.33614142B ->143B 0.19920

Excited State 3: 2.035-A 1.8836 eV 658.23 nm f=0.0106 <S**2>=0.785136B ->143B 0.13152137B ->143B -0.20716138B ->143B 0.68537139B ->143B -0.15388140B ->143B 0.30655141B ->143B 0.58487

Excited State 4: 2.030-A 1.9420 eV 638.44 nm f=0.0051 <S**2>=0.781138B ->143B -0.55564139B ->143B 0.41012140B ->143B 0.18921141B ->143B 0.68961

Excited State 5: 2.037-A 2.0585 eV 602.31 nm f=0.1786 <S**2>=0.788143A ->146A -0.10606137B ->143B 0.24088138B ->143B 0.40408139B ->143B 0.82941140B ->143B 0.10650141B ->143B -0.21397

Excited State 6: 2.034-A 2.0695 eV 599.09 nm f=0.0988 <S**2>=0.785137B ->143B 0.88974139B ->143B -0.30287140B ->143B 0.26822142B ->143B -0.14939

3Meb

3iPrb

15

4.3 Spin density distribution

Figure S9. Spin density distribution of the optimized structure of 3Mea, calculated at the UB3PW91/6-31G(d) level.

Figure S10. Spin density distribution of the optimized structure of 3iPra, calculated at the UB3PW91/6-31G(d) level.

16

Figure S11. Spin density distribution of the optimized structure of 3Meb, calculated at the UB3PW91/6-31G(d) level.

Figure S12. Spin density distribution of the optimized structure of 3iPrb, calculated at the UB3PW91/6-31G(d) level.

17

4.4 The atoms in molecules (AIM)

Figure S13. Atom in Molecules (AIM) analysis based on X-ray geometries of 2Mea-b, 2iPra-b, 3Mea and 3iPra showing bond paths between the central nitrogen and the carbonyl oxygen, calculated at the RCAM- and UCAM-B3LYP-D3/def2-SVP levels in 2 and 3, respectively. Table S10. Summary of the electron density (r(r) e/ao3), Laplacian (Ñ2r(r) e/ao5) at the bond critical point (bcp) of the N-O bonds, and AIM analysis along with kinetic energy density G(r), potential energy density V(r), and energy density H(r) at the (3, –1) critical point in between N and O based on X-ray geometry.




r (N-O1) 0.016029 0.014962 – 0.016690 – 0.013793

Ñ2r (N-O1) 0.058460 0.052404 – 0.064195 – 0.052479

r (N-O2) 0.013945 0.013607 – 0.016114 – 0.013087

Ñ2r (N-O2) 0.051214 0.048605 – 0.062402 – 0.048313

V (potential, N-O1) –0.011815 –0.011446 – –0.012760 – –0.010524

G (kinetic, N-O1) 0.013215 0.012274 – 0.014404 – 0.011822

H (total, N-O1) 0.001400 0.000827 – 0.001644 – 0.001298

|V|/G (N-O1) 0.894 0.933 – 0.886 – 0.890

G/r (N-O1) 0.824 0.820 – 0.863 – 0.857

H/r (N-O1) 0.087 0.055 – 0.099 – 0.094

V (potential, N-O2) –0.010297 –0.010535 – –0.012367 – –0.009938

G (kinetic, N-O2) 0.011550 0.011343 – 0.013984 – 0.011008

H (total, N-O2) 0.001253 0.000808 – 0.001617 – 0.001070

|V|/G (N-O2) 0.892 0.929 – 0.884 – 0.903

G/r (N-O2) 0.828 0.868 – 0.868 – 0.841

H/r (N-O2) 0.090 0.062 – 0.100 – 0.082

18

Figure S14. Atom in Molecules (AIM) analysis based on fully optimized geometries of 2Mea-b, 2iPra-b, 3Mea and 3iPra showing bond paths between the central nitrogen and the carbonyl oxygen, calculated at the RCAM- and UCAM-B3LYP-D3/def2-SVP levels in 2 and 3, respectively. Table S11. Summary of the electron density (r(r) e/ao3), Laplacian (Ñ2r(r) e/ao5) at the bond critical point (bcp) of the N-O bonds, and AIM analysis along with kinetic energy density G(r), potential energy density V(r), and energy density H(r) at the (3, –1) critical point in between N and O based on fully optimized geometry.




r (N-O1) 0.016943 0.015888 0.014791 0.016275 0.012671 0.012714

Ñ2r (N-O1) 0.061432 0.057241 0.050928 0.062634 0.047075 0.047472

r (N-O2) 0.016889 0.015873 0.014641 0.016165 0.012601 0.012642

Ñ2r (N-O2) 0.061145 0.057130 0.050375 0.062058 0.047001 0.047369

V (potential) –0.012547 –0.012277 –0.011199 –0.012377 –0.009665 –0.009629

G (kinetic) 0.013953 0.013280 0.011965 0.013946 0.010717 0.010736

H (total) 0.001405 0.001003 0.000767 0.001569 0.001052 0.001107

|V|/G 0.899 0.924 0.936 0.887 0.902 0.897

G/r 0.823 0.837 0.809 0.863 0.846 0.849

H/r 0.0829 0.0632 0.0519 0.0971 0.0830 0.0876

Atoms in Molecules (AIM) analysis based on fully optimized geometries of 2Mea-b, 2iPra-b, 3Mea and 3iPra showed bond paths between the central nitrogen atom and the ester oxygen atoms in both cation radical and neutral species. The observed 12-N-5 weakly coordinating interaction in neutral compounds may due to the effective delocalization of the lone pair on nitrogen atom and the residue positive charge on nitrogen then can form electrostatic interactions with the adjacent oxygen electron pairs, forming a nO®π*NC interaction as we explained in text.

19

4.5 The energy difference between sp2 carbonyl (CO) and alkoxyl (OR) coordination modes

Table S12. Single Point (SP) Calcs. at B3LYP-D3/6-31+G* levels for the energy difference between sp2 carbonyl (CO) and alkoxyl (OR) coordination modes. [a,b]

Carbonyl oxygen [kcal/mol] Alkoxyl oxygen

[kcal/mol] Difference [kcal/mol]

2Mea –1431986.818 –1431988.364 1.55

2Meb –1278208.598 –1278209.961 1.36

2iPra –1530690.305 –1530689.352 –0.95

2iPrb –1376912.023 –1376911.236 –0.79

3Mea –1431860.742 –1431860.633 –0.11

3Meb –1278074.77 –1278074.30 –0.47

3iPra –1530564.449 –1530562.042 –2.40

3iPrb –1376778.493 –1376775.592 –2.90

[a] RB3LYP-D3/6-311G* (neutral) and UB3LYP-D3/6-311G* (cationic) levels for geometry optimization and frequency analysis. [b] IEFPCM (CH2Cl2 solvent) for solvent effects.

Figure S15. Relaxed potential energy scan for the rotation of single COOR group of 2iPra and 3iPra at the RCAM- and UCAM-B3LYP-D3/def2-SVP levels, respectively. The other COOR group is carbonyl coordination. Vertical axis shows the relative energy E to the total energy at the lowest local minimum structure. Dotted line shows the relative energy for the local minimum where both COOR groups are alkoxyl coordination. Note that X-ray geometries were carbonyl coordination for 2iPra and alkoxyl coordination for 3iPra, whereas the calculated lowest minimum geometries are predicted to be carbonyl coordination for both systems.

C4C9

OR

O10

C3

N

20

4.6 Examination of applicability of CAM-B3LYP-D3 density for the population and topological analyses Examination of applicability of CAM-B3LYP-D3 density for the population and topological analyses in comparison with the results from DLPNO-CCSD linearized density by employing simplified models 2x and 3x.

Figure S16. Structure of simplified model 2x/3x (carbonyl coordination). Table S13. Selected calculated bond lengths (Å), angles and dihedral angles [°] for 2x and 3x at the RCAM- and UCAM-B3LYP-D3/def2-SVP levels in 2x and 3x, respectively.

Parameters Ionic radical Neutral

3x 3x 2x 2x

Coord. (CO) (OH) (CO) (OH)

N-O1 2.534 2.644 2.877 2.795

N-O2 2.534 2.644 2.877 2.795

N-C1 1.435 1.408 1.376 1.384

N-C2 1.457 1.452 1.450 1.447

N-C3 1.457 1.452 1.450 1.447

SNa 360.0 360.0 360.0 360.0

FOCCO 3.2 47.8 59.3 69.31

Figure S17. Difference of CAM-B3LYP-D3/def2-SVP density and DLPNO-CCSD/def2-SVP linearized density, ρ(CAM-B3LYP-D3) – ρ(DLPNO-CCSD) (for CO coordination, left: 3x, right: 2x:). Yellow/blue surfaces in isosurface maps represent positive and negative region of with contour values of ±0.005 a.u. For ionic radical species, ROHF-DLPNO-CCSD method is employed. Table S14. Comparison of CAM-B3LYP-D3/def2-SVP and DLPNO-CCSD/def2-SVP (linearized density) results for NPA charges and AIM analysis (for CO coordination).

Ionic radical 3x Neutral 2x

CAM-B3LYP DLPNO-CCSD CAM-B3LYP DLPNO-CCSD

Coord. (CO) (CO) (CO) (CO)

q(N) -0.087 -0.058 -0.492 -0.488

q(O1) -0.622 -0.582 -0.621 -0.573

q(O2) -0.622 -0.582 -0.621 -0.573

q(C1) 0.187 0.163 0.283 0.256

q(C2) -0.426 -0.381 -0.405 -0.353

q(C3) -0.426 -0.381 -0.405 -0.353

r (N-O1) 0.02220 0.02244 0.01268 0.01303

Ñ2r (N-O1) 0.08266 0.08319 0.04599 0.04687

r (N-O2) 0.02219 0.02243 0.01267 0.01303

Ñ2r (N-O2) 0.08261 0.08314 0.04599 0.04687

21

4.7 The comparison of optimized two electron oxidation species vs optimized one electron oxidation species We optimized the geometries of two electron oxidized species (4Mea-b, 4iPra-b). Results are listed in Table S15. In Table S16 and S17, we also listed the results of cationic radical and neutral species. Because of some difficulties in the optimizations, we could not have obtained yet the optimized geometries of 4Meb (CO) and 4iPra (OiPr). Changes in the geometric parameters by oxidization, such as dihedral angle FOCCO, are found to be not monotonic. However, some systems of alkoxyl coordination type (4Meb and 4iPrb) are found to have very large dihedral angle of FOCCO.

Table S15. Selected calculated bond lengths (Å), angles and dihedral angles [°] for 4Mea-b, 4iPra-b optimized at the RCAM-B3LYP-D3/def2-SVP level.

ParParameters

Dicationic Dicationic

4Mea 4Meb 4iPra 4iPrb

Coord. (CO) (OMe) (CO) (OMe) (CO) (OiPr) (CO) (OiPr)

N-O1 2.650 2.676 –a) 2.823 2.732 –a) 2.848 2.931

N-O2 2.648 2.677 –a) 2.813 2.747 –a) 2.853 2.901

N-C1 1.438 1.423 –a) 1.378 1.420 –a) 1.382 1.370

N-C2 1.359 1.364 –a) 1.385 1.365 –a) 1.382 1.389

N-C3 1.359 1.364 –a) 1.386 1.364 –a) 1.381 1.390

SNa 360.0 360.0 –a) 360.0 360.0 –a) 360.0 360.0

FOCCO 37.4 62.7 –a) 91.3 60.5 –a) 72.3 98.8

a) Geometry optimization has not been completed primarily due to the difficulty of convergence.

Table S16. Selected calculated bond lengths (Å), angles and dihedral angles [°] for 3Mea and 3iPra at the UCAM-B3LYP-D3/def2-SVP level.

ParParameters

Cationic radical Cationic radical



N-O1 2.686 2.654 –a) 2.652 2.732 2.676 2.787 –a)

N-O2 2.684 2.656 –a) 2.654 2.731 2.673 2.788 –a)

N-C1 1.435 1.434 –a) 1.433 1.431 1.439 1.424 –a)

N-C2 1.388 1.388 –a) 1.390 1.388 1.388 1.393 –a)

N-C3 1.387 1.388 –a) 1.390 1.388 1.387 1.393 –a)

SNa 360.0 360.0 –a) 360.0 360.0 360.0 360.0 –a)

FOCCO 39.1 54.1 –a) 55.2 57.4 47.0 66.4 –a)


Table S17. Selected calculated bond lengths (Å), angles and dihedral angles [°] for 2Mea and 2iPra at the RCAM-B3LYP-D3/def2-SVP level.

ParParameters

Neutral Neutral



N-O1 2.826 2.734 2.795 –a) 2.885 2.747 2.882 2.729

N-O2 2.824 2.734 2.802 –a) 2.889 2.806 2.886 2.796

N-C1 1.416 1.417 1.420 –a) 1.416 1.422 1.419 1.425

N-C2 1.405 1.405 1.403 –a) 1.408 1.398 1.405 1.394

N-C3 1.405 1.405 1.401 –a) 1.407 1.413 1.404 1.413

SNa 360.0 360.0 360.0 –a) 360.0 359.9 360.0 360.0

FOCCO 61.4 67.2 56.3 –a) 73.6 75.0 74.4 71.3


22

We have also performed the AIM analysis for the (3, –1) critical point of the two-electron oxidized species (Figure S18; experimentally two-electron oxidation is not possible, cf. CV data). Please note that, as mentioned in the previous reply, we could not obtain the optimized geometries of 4Meb (CO) and 4iPra (OiPr) despite of much effort.

We have found that for 4Meb (OMe), 4iPrb (CO) and 4iPrb (OiPr), (3, –1) critical points between N and O could not be obtained, whereas those between C and O atoms were obtained. These results indicate that the weak attractive interaction between N atom and O atom may not be observed even in their corresponding dication diradical species (10-N-5), which are considered to have 3-center-4-electron hypervalent bond. In Table S18, we summarized several important values obtained from the AIM analysis.

Figure S18. Atom in Molecules (AIM) analysis of 4Mea-b and 4iPra-b calculated at the RCAM -B3LYP-D3/def2-SVP levels.

Table S18. Summary of AIM analysis along with kinetic energy density G(r), potential energy density V(r), and energy density H(r) at the (3, –1) critical point in between O1 and X (X = N or C) for two electron oxidized species.

Parameters Dicationic Dicationic


Coord. (CO) (OMe) (CO) (OMe)b) (CO) (OiPr) (CO) b) (OiPr) b)

r (X-O1) 0.017838 0.016007 –a) 0.014827 0.015295 –a) 0.014249 0.011407

Ñ2r (X-O1) 0.066352 0.063469 –a) 0.051968 0.057455 –a) 0.050160 0.040642

V (potential) –0.013053 –0.012153 –a) –0.010821 –0.011129 –a) –0.010070 –0.007783

G (kinetic) 0.014820 0.014010 –a) 0.011906 0.012747 –a) 0.011305 0.008972

H (total) 0.001767 0.001857 –a) 0.001086 0.001617 –a) 0.001235 0.001189

|V|/G 0.881 0.867 –a) 0.736 0.873 –a) 0.891 0.867

G/r 0.831 0.875 –a) 0.803 0.833 –a) 0.793 0.787

H/r 0.0991 0.116 –a) 0.0732 0.106 –a) 0.0867 0.104

a) Geometry optimization has not been completed primarily due to the difficulty of convergence. b) Results of (3, -1) critical point in between O1 and C.

23

5.p-donating methoxy derivative (2Mec)

During revision, in response to reviewers’ suggestions on the N-O interactions, we have carried out additional experimental work to synthesize the neutral π-donating methoxy derivative (2Mec) as a comparison in addition to the electron-withdrawing substituted derivatives reported in the MS. Since our aim was to enforce the hypervalent bonding (in the 11-N-5 radical cations), we had only electron-withdrawing substituents on the aryl groups initially. AIM on N-O (3, –1) critical points were analyzed based on optimized geometry (Figure S14, Table S11) as well as solid-state geometries (single point calculations based on X-ray structures, Figure 3 and Table 10).

Figure S19. (a) Solid-state molecular structures of 2Mec. Thermal ellipsoids are set at 30% probability. Ellipsoids of periphery atoms, hydrogen atoms, and counter ions are omitted for clarity. CCDC number: 1988910. (b) AIM analysis of 2Mec based on optimized geometry. (c) AIM analysis of 2Mec based on X-ray geometry.

Table S19. Selected experimental and calculated bond lengths (Å), angles, dihedral angles at the RCAM-B3LYP-D3/def2-SVP level of 2Mec and its summary of AIM analysis along with kinetic energy density G(r), potential energy density V(r), and energy density H(r) at the (3, -1) critical point in between O1 and N.

Parameters

2Mec

optimized X-ray

Coord. (OMe) (OMe)

N-O1 2.765 2.939(2)

N-O2 2.767 3.051(19)

N-OAve 2.766 2.995(19)

N-C1 1.411 1.410(2)

N-C2 1.410 1.415(2)

N-C3 1.410 1.425(2)

SNa 360.0 359.9(38)

FOCCO 73.94 112.8

r (N-O1) 0.014966 0.010913

Ñ2r (N-O1) 0.053428 0.039661

V (potential) –0.011569 –0.008410

G (kinetic) 0.012463 0.009163

H (total) 0.000894 0.000752

|V|/G 0.928 0.917

G/r 0.833 0.840

H/r 0.0597 0.0689

The optimized structures significantly underestimate the N-O distances for 2Meb and 2Mec, showing the N-O (3, –1) critical points on both sides in all neutral and cationic radical structures (Figures S14 and S19). In contrast, the AIM analysis based on solid-state structures showed both N-O (3, –1) critical points in cationic radical species and two of the neutral amines

24

(2Mea and 2iPrb). These structures also exhibit shorter N-O distances than 2Meb, 2Mec and 2iPra. The latter structures showed no or only one (3, –1) critical point. The AIM based on X-ray solid-state structures are more reflective than the optimized structures, as the latter are based on significantly shorter N-O distances. The longer N-O distances observed in the solid-state structures are likely due to crystal-packing effect, which means if any N-O attractive interaction exists, it is weaker than crystal-packing effect. Overall, these results suggest that the N-O interactions may not exit in all neutral amine species and if they do, they are very weak.

In addition, comparing the para-Cl (2Mea) and para-OMe (2Mec) with same N-O coordination modes, the π-donating OMe derivative showed significantly longer N-O distances and weaker N-O interaction on only one side. However, since we cannot determine how much crystal packing effect contribute to the solid-state structure, we cannot conclude on the OMe π-donating effect on the nO®p*NC stabilization, which was the original target reason for synthesizing para-OMe (2Mec). Therefore, the results on 2Mec is not reported in the MS but in ESI only. Synthesis of dimethyl 2-(bis(4-methoxyphenyl) amino)-5-(tert-butyl) isophthalate (2Mec) Bis(4-methoxyphenyl) amine (700 mg, 3.03 mmol) was coupled with dimethyl 2-bromo-5-tert-butyl-isophthalate (1Me) (1.0 g, 3.03 mmol) according to the above Ullmann procedure (19 mL of n-Bu2O) for 96 h at 145 °C. The crude product was purified by flash chromatography using a 1:10 solution of ethyl acetate / hexane as the eluent to give 462 mg (0.968 mmol,32% yield) of the title compound as a yellow solid. 1H NMR (400 MHz, CDCl3) δ (ppm) δ 7.69 (s, 2H), 6.88 (d, J = 8.0 Hz, 4H), 6.74 (s, 4H), 3.74 (s, 6H), 3.50 (s, 6H), 1.33 (s, 9H). 13C NMR (100 MHz, CDCl3) δ (ppm) δ 168.5, 154.8, 147.7, 142.4, 141.3, 131.6, 130.8, 123.5, 114.2, 55.5, 52.2, 34.7, 31.2. MS(ESI) m/z [M+Na]+ C28H31O6NNa Calcd for: 500.20436 Found: 500.20422. Elemental analysis: Calcld.: C, 70.42; H, 6.54; N, 2.93; Found: C, 70.10; H, 6.24; N, 2.72. M.P.: 94.3-95.4 °C. Crystal data:Formula: C28H31NO6; Mol wt: 477.54; Crystal system: Monoclinic; Space group: P21/c; a, Å: 10.3036(6); b, Å: 18.9257(11); c, Å: 13.0352(7); α, deg: 90; β, deg: 94.843(2); γ, deg: 90; V, Å3: 2532.8(2); Z: 4; Dcalc, Mg/m3: 1.252; Abs coeff, mm−1: 0.088; F(000): 1016; Temp, K:173(2); Reflections:26160; Independent: 5792; Rint: 0.0463; Parameters: 323; R1 [I > 2σ(I)]: 0.0510; wR2 (all data): 0.1593.

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6. NMR spectra

2-Bromo-5-tert-butyl-1,3-dimethylbenzene (b) 1H NMR (400 MHz, CDCl3) δ (ppm) 7.11 (s, 2H), 2.43 (s, 6H), 1.31 (s, 9H).

13C NMR (100 MHz, CDCl3) δ (ppm) 149.8, 137.8, 125.6, 124.6, 34.3, 31.4, 24.2.

26

2-Bromo-5-tert-butyl-isophthalic Acid (c) 1H NMR (400 MHz, DMSO) δ (ppm) 13.60 (s, 2H), 7.68 (s, 2H), 1.28 (s, 9H).

13C NMR (100 MHz, DMSO) δ (ppm) 168.3, 150.7, 136.6, 127.8, 113.3, 34.6, 30.6.

27

Dimethyl 2-Bromo-5-tert-butyl-isophthalate (1Me) 1H NMR (400 MHz, CDCl3) δ (ppm) 7.68 (s, 2H), 3.93 (s, 6H), 1.30 (s, 9H).

13C NMR (100 MHz, CDCl3) δ (ppm) 167.6, 150.9, 135.1, 129.6, 115.8, 77.48, 52.8, 34.8, 34.0.

28

Diisopropyl 2-bromo-5-(tert-butyl) isophthalate (1iPr) 1H NMR (400 MHz, CDCl3) δ (ppm) 7.59 (s, 2H), 5.32 – 5.22 (m, 2H), 1.38 (d, J = 4 Hz, 12H), 1.30 (s, 9H).

13C NMR (100 MHz, CDCl3) δ (ppm) 166.9, 150.8, 135.9, 128.9, 115.0, 70.0, 34.8, 30.9 21.8.

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Dimethyl 2-(bis(4-chlorophenyl) amino)-5-(tert-butyl) isophthalate (2Mea) 1H NMR (400 MHz, CDCl3) δ (ppm) 7.81 (s, 2H), 7.14 (d, J = 4 Hz, 4H), 6.87 (d, J = 4 Hz, 4H), 3.54 (s, 6H), 1.36 (s, 9H).

13C NMR (100 MHz, CDCl3) δ (ppm) 167.6, 149.8, 145.5, 141.1, 132.1, 131.4, 129.1, 127.3, 123.3, 52.5, 35.0, 31.2.

30

Dimethyl 2-(bis(4-(trifluoromethyl) phenyl) amino)-5-(tert-butyl) isophthalate (2Meb) 1H NMR (400 MHz, CDCl3) δ (ppm) 7.91 (s, 2H), 7.45 (d, J = 8 Hz, 4H), 7.04 (d, J = 8 Hz, 4H), 3.53 (s, 6H), 1.38 (s, 9H).

13C NMR (100 MHz, CDCl3) δ (ppm) 167.1, 151.0, 149.2, 140.4, 132.3, 131.7, 126.3 (q, 3J C-F = 10 Hz), 124.4 (q, 1J C-F = 270 Hz), 124.3 (q, 2J C-F = 30 Hz), 121.7, 52.6, 35.1, 31.1.

19F NMR (376 MHz, CDCl3) δ (ppm) -62.29.

31

Diisopropyl 2-(bis(4-chlorophenyl) amino)-5-(tert-butyl) isophthalate (2iPra) 1H NMR (400MHz, CDCl3) δ (ppm) 7.73 (s, 2H), 7.12 (d, J = 8 Hz, 4H), 6.90 (d, J = 8 Hz, 4H), 4.85 (m, 2H), 1.36 (s, 9H), 1.04 (d, J =8 Hz, 12H).

32

13C NMR (100 MHz, CDCl3) δ (ppm) 166.5, 149.9, 145.3, 140.6, 133.4, 130.4, 128.9, 126.9, 123.1, 69.5, 34.9, 31.2, 21.6.

Diisopropyl 2-(bis(4-(trifluoromethyl) phenyl) amino)-5-(tert-butyl) isophthalate (2iPrb) 1H NMR (400 MHz, CDCl3) δ (ppm) 7.80 (s, 2H), 7.44 (d, J = 8 Hz, 4H), 7.07 (d, J = 8 Hz, 4H), 4.85 (m, J = 24 Hz, 2H), 1.38 (s, 9H), 0.99 (d, J = 4 Hz, 12H).

33

13C NMR (100 MHz, CDCl3) δ (ppm) 166.1, 150.9, 149.1, 140.1, 133.4, 130.7, 126.2 (q, 3J C-F = 10 Hz), 124.5 (q, 1J C-F = 270 Hz), 124.0 (q, 2J C-F = 30 Hz), 121.6, 69.7, 35.0, 31.2, 21.4.

19F NMR (376 MHz, CDCl3) δ (ppm) -62.45.

34

Dimethyl 2-(bis(4-methoxyphenyl)amino)-5-(tert-butyl) isophthalate (2Mec) 1H NMR (400 MHz, CDCl3) δ 7.69 (s, 2H), 6.88 (d, J = 8.0 Hz, 4H), 6.74 (s, 4H), 3.74 (s, 6H), 3.50 (s, 6H), 1.33 (s, 9H).

13C NMR (100 MHz, CDCl3) δ 168.5, 154.8, 147.7, 142.4, 141.3, 131.6, 130.8, 123.5, 114.2, 55.5, 52.2, 34.7, 31.2.

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